Two component convoluted filaments



A. L. BREEN ETAL TWO COMPONENT CONVOLUTED FILAMENTS Jan. 23, 1962 3 Sheets-Sheet 1 Filed Aug. 1, 1957 INVENTORS A LVIN L. BREEN WALTER E. JORDAN 2 fwd ATTORNEY Jan. 23, 1962 A. BREEN ETAL 3,017,636

TWO COMPONENT CONVOLUTED FILAMENTS Filed Aug. 1 1957 Eig,.5

5 Sheets-Sheet 2 INVENTORS VIN L. BREEN WAL E. JORDAN ATTORNEY Jan. 23, 1962 A. L. BREEN ETAL 3,017,686

TWO COMPONENT CONVOLUTED FILAMENTS Filed Aug. 1, 1957 5 Sheets-Sheet 3 Ijig, 10 Eig,.11 i .12

Eig,.13

INVENTORS WALTER E. JORDAN BY @mwe QGZMM ALVIN L. BREEN 36 ATTORNEY TWO COWONENT CONVOLUTED FILAMENTS Alvin L. Breen, West Chester, Pa., and Walter E. Jordan,

Wilmington, Del., assignors to E. I. du. Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware Filed Aug. 1, 1957, Ser. No. 675,727 3 Claims. (6i. 28-82) This invention relates to a novel fiber structure affording high bulk yarns and it is particularly concerned with filaments composed of synthetic linear polymers, especially as components of multi-component filaments.

Investigators in the textile field have long been concerned with obtaining voluminous strands of continuous filaments with properties similar to those yarns obtained from natural staple fibers. Production of staple fiber yarn (also called spun yarn) is quite expensive and requires a complex series of operations involving aligning the fibers, combining them into an elongated band and drawing the bundle to smaller diameter while twisting to prevent excessive slippage of adjacent fibers past each other, together with still further operations required to produce a yarn or thread useful for textile purposes.

Synthetic fibers are produced directly as continuous filaments by an extrusion-spinning process. Strands or yarn can be made merely by combining the continuous filaments and without the time-consuming and expensive processing steps required for the making of spun yarn from staple fibers. The continuous filament yarn can be made very strong because of the absence of loose ends found in staple yarn that are unable to transmit imposed stresses. However, due to their lack of loose ends and their cross-sectional and longitudinal uniformity, conventional continuous filament yarns are more compact and dense than their staple counterparts since the continuous filaments lie close together in the yarn. This compactness, when the yarns are made into fabric, e.g., woven or knitted fabric, limits the amount of insulating air space present, reduces the visual covering power of a given weight of fabric and imparts to the fabric a hard slick hand typical of synthetic continuous filaments.

Bulky continuous filament yarns have been made by heat setting a highly twisted yarn of, for example, nylon, at least partially untwisting the yarn with, if necessary, further twist in the opposite direction and then plying two ends of opposite twists. Such a process is very expensive and, while affording a voluminous yarn, is too elastic for many textile applications.

It has also been proposed to make a voluminous continuous filament yarn by mechanically crimping the yarn, for example, by a hot stuffing box process. Such a product, while more voluminous than uncrimped continuous filament yarn, has the disadvantage that it must be fabricated in the bulky form and the further drawback that it loses an appreciable amount of its bulk due to the crimp being pulled out by the tensions encountered in fabric formation.

Self-crimping filaments have also been proposed. It has been suggested, for example, to spin two different fiber-forming materials in a side-by-side arrangement followed by drawing of the composite fiber to impart a difference in shrinkability between the components when relaxed under shrinking conditions. Upon shrinking, such filaments become crimped with from about 1 to 30 helical crimps per inch. Yarns made of such filaments have the disadvantage for many applications of being elastic. Also, they do not develop the desired bulk because adjacent filaments will crimp together in a followthe-leader manner such as may be observed, for example, in crimped staple chips and thus each filament will ted fitates Patent not exist as a separate and distinct crimped structure. Furthermore, the relatively coarse crimp permits the filaments to pack together readily in processing Other procedures for imparting crimp have been proposed, but have resulted likewise in products having a relatively coarse crimp and subject to the disadvantages recited above.

it is an object of this invention to provide novel, nonround filaments which may be continuous filaments or staple fiber and which are preferably of textile denier (i.e., 1 to 10 denier per filament), and which have a low apparent density. A further object relates to novel, bulky non-round multi-component filaments. A still further object relates to multi-component filaments of low density having a novel and critical arrangement of components. Other objects will appear hereinafter.

The objects of this invention are accomplished by the preparation of a multi-component non-round filament having at least one hydrophobic synthetic linear polymer component and having a stem or root and at least one fin Whose width is at least 1.4 times its thickness, the fin or fins of which have an average angular displacement of at least 0.1/ i (01 per micron). A displacement of 0.3/ .t is equal, for example, to 20 complete turns per inch in the case of a helical convolution around a stem. The filament comprises at least two linear polymer components. At least about of the stem is made up of one of these components, and at least about 60% of the fin is made up of the other component. Preferably, the component comprising 60% of the fin is concentrated in that part of the fin farthest from the stem (or center of gravity).

The term synthetic linear polymer, as used herein, signifies a polymer synthesized from monomeric materials, e.g., by condensation or by addition reaction (as distinct from natural polymers such as cellulose, for example). Synthetic linear polymers, particularly those suitable for use as textile filaments and yarns have properties widely different from natural polymers, both chemically and physically, e.g., the former are far less water absorptive.

The term hydrophobic as applied to synthetic linear polymers, when used herein, signifies the characteristic of absorbing not more than about 8% of its dry weight of water when filaments or yarns composed of such polymer are exposed to an atmosphere of relative humidity at F. This is the moisture regain of the filament.

The term textile filament denier, as used herein, signifies a denier of from 1 to 10 per filament.

In referring herein to the cross section of a filament, it will be understood that the cross sections are perpendicular to the filament axis.

The term ruffle as used herein signifies (unless otherwise indicated) a sinuous conformation of the fin, analogous to the ruffle on a window curtain.

The term convolution as used herein (unless otherwise indicated) comprehends not only rufiles but also spiral or helical turns of the fins about the filament stem. By the practice of the invention either ruflies or spiral convolutions or both together are imparted to filaments.

The expression convolutions per inch as used herein represents the number of complete (360) cycles of a projection of a fin, whether in the form of rufiles or helices, as viewed longitudinally per inch of length of the filament.

The term fin as used herein (unless otherwise indicated) signifies, with respect to cross-sectional area (although the fin will proceed lengthwise of the filament), that part of a non-round filament enscribed by (l) a line (termed fin base line") drawn through the cross-sectional center of gravity (which may also be termed the center of area) of the filament normal to the line that determines the width of the fin (i.e., cross-sectional length as described below) and (2) the periphery of the filament intercepting said fin base line. Thus, although the term fin would normally be considered as comprising only the Web or extension to the filament, it also includes a portion of the filament stem or root for the purpose of description.

By the term width of the fin is meant the length of the longest straight line (termed width line) that can be drawn within the periphery of the fin cross section from the center of area to the tip of the fin, assuming the fin to be straightened out normal to its base line. Many fins are not straight and the line for determining width would not be straight if drawn within many actual fins.

By the term thickness of the fin is meant the average distance across the fin periphery as measured normal to said width line.

By the term stem of the filament is meant the root or body of the filament from which the fin webs protrude. The stem will, of course, include a portion of the fin as defined above, although, from a practical standpoint, the physically protruding fin (as distinct from the fin as defined above) is distinct from the stem.

By angular displacement is meant the total angle (in degrees) swept out, without regard to direction, by width lines between two spaced points along the filament axis, said angle being measured by projecting the width lines, between the two points, on the plane of a width line perpendicular to the filament axis at one of said points. The angular displacements referred to herein are determined from measurements on cross-sectional and longitudinal photomicrographs of the filaments. The longitudinal photomicrographs are used to measure the angle at which a fin crosses over the stem. It will be understood that angular displacement data and rufiles per inch will not be absolutely equivalent for all samples due to differences in sampling.

FIGURE 1 is an axial longitudinal section of a spinneret assembly which can be used to make the composite filaments of this invention. FIGURE 2 is a transverse cross section of the apparatus of FIGURE 1 taken at 22 thereof and showing a plan of the front or bottom spinneret plate. FIGURE 3 is a transverse cross section taken at 3-3 of FIGURE 1 to show the plan of the top of that plate thereof.

FIGURE 4 is a greatly magnified (200 times) view of a form of spinneret orifice useful in making the composite filaments of this invention.

FIGURE 5 is a sectional elevation of a spinneret plate and back plate useful for making composite flat filaments of this invention. FIGURE 6 is a plan view of the spinneret plate of FIGURE 5 taken along line 6-6 of FIG- URE 5. FIGURE 7 is a plan view of FIGURE 5 showing the top of the back plate through which spinning polymer is fed to the spinneret plate. FIGURE 8 is a sectional elevation taken along line 88 of FIGURE 6. FIGURE 9 is a sectional elevation taken along line 99 of FIGURE 6.

FIGURE 10 is a view of a longitudinal portion of a filament, greatly magnified, having one form of convolution, i.e., ruffles characteristic of the filaments of this invention, and FIGURE 11 is a view of a longitudinal portion of a filament, greatly magnified, having a different form of convolution, i.e., spirals or helices characteristic of the filaments of this invention.

FIGURES 12 and 13 are cross-sectional views, greatly magnified, respectively, of Y-shaped filaments and of flat (or ribbon-shaped) filaments made in accordance with this invention.

FIGURE 14 represents one-half of a convolution of a filament of this invention, greatly magnified, in perspective, with provision illustrated thereon for measuring angular displacement of a fin.

An understanding of angular displacement and its measurement can readily be obtained by reference to FIG- URE 14 of the drawings. This figure is drawn in perspective in which the lines are approximately 30 to the horizontal so as to show the development of the fin convolution, i.e., a rufile in this case. The filament is of keyhole cross-sectional shape such as may be obtained by use of a keyhole spinning orifice shown in FIGURE 15 and has the general appearance of the filament shown in FIGURE 10 of the drawings. For convenience, in this figure the cross-sectional end of this filament shows the fin in vertical position.

FIGURE 14 is a greatly magnified view of a short length of filament having one-half a complete convolution or ruffie of the fin (in this case one-half a complete sine wave). In this figure, the center of gravity or center of area of the filament cross section is designated as 27 and a line 28, 29 (the fin base line) is drawn, as shown, through 27. A line 30, 31 is drawn from the center of the fin tip through 27, this line being the longest line that can be drawn through the fin and lines 28, 29 and 30, 31 are drawn perpendicular to each other. The fin 32 is shown as one-half a complete convolution, the other half (not shown) being in reverse in this case to that shown. Where the convolution is a helix, the other half of the helix obviously proceeds in the same direction rather than in the opposite direction.) Vertical plane 33, 34, 35, 36 is drawn through line 30, 31 and through the filament center of gravity axis 27, 37. Midway of the one-half fin convolution shown in FIGURE 14, a line 54, 55 (fin width line) is drawn from line 27, 37 to the tip of fin 32, the angle 56 subtended by plane 33, 34, 35, 36 and this line being the angular displacement. In FIGURE 14, the length of filament from the left-hand side of the figure from 0 displacement to the center point (where a value of for angle 56 was measured) is 20 microns (0.02 mm.) giving an angular displacement of 4.0//.L (300 complete convolutions per inch). The angular displacement per micron of length that is referred to herein indicates the degree and intensity of convoluting characteristics of the filaments of this invention. It will be understood that if lines were drawn from the line of origin 27, 37 to the tip of fin 32 between the beginning of the filament section shown in FIGURE 14 and point 37, the angular displacement would be correspondingly I6OO/4O/L or 4.0/,u.

Reference has been made in the above descriptions, in connection with FIGURE 14 of the drawings, to rufiles as one form of convolution characteristic of the filaments of this invention. A filament showing ruffles along a continuous length is illustrated in FIGURE 10 of the drawings.

In addition to the ruffles just referred to, the filaments of this invention may, as stated, alternatively assume a spiral or helical convolution along the axis of the filament as shown in FIGURE 11 of the drawings, which like FIGURE 10, represents a greatly magnified view of the filament.

Both the ruffie referred to in FIGURES l4 and 10 and the spiral convolution shown in FIGURE 11 are to be distinguished from the crimps of the prior art which merely represent either the approximate folding back of filaments upon themselves or upon adjacent filaments, as in the stutter-box type of crimping or in mechanical gear crimping, or the helical type of crimp (which may reverse itself) in which the filaments spiral in helical or coiled spring-like fashion around a core of air.

It is to be understood that the convolutions which characterize the filaments of this invention may reverse themselves at regular or irregular intervals, not only in the sense of reversal to complete a 360 path for one ruffle or convolution as described with respect to FIG- URE 14, but by actual change in direction along the filament at intervals. Nevertheless, the total number of rufi'les or convolutions, as designated herein in the examples, will include all regardless of direction of fin distortion. The number of ruffles per inch (i.e., the angular displacement) is a measure of the volume or space effectively swept by a filament.

In the examples, the relative viscosity (in), i.e., the viscosity of a solution of polymer relative to that of the solvent is used as a measure of the molecular weight. An 8.2:.2% solution of the polymer in an appropriate solvent at 25 C. is used as a standard for measuring relative viscosity. in the case of polyamides, the solution contains 5.5 grams of polymer in 50 ml. of 90% formic acid and, in the case of polyesters, the solution contained 2.15 grams of the polymer in 20 ml. of a 7/ 10 mixture of trichlorophenol/phenol.

By the expression draw ratio is meant the ratio between the initial undrawn (as-spun) length of yarn or filament and the final permanently drawn length of yarn or filament. It will be understood that reference to permanently drawn length means the length of the filament assumed by release of the drawing force; permanently drawn filaments always have a certain elongation prior to breakage, which elongation is temporary and is lost upon removal of the force causing the filament to elongate.

Referring to FIGURE 1, front or bottom plate 1 with orifices 2 is recessed at the back about plateau-like protrusions 4. Each orifice consists of capillary 21 at the exit (which, in the present case, is of a non-round shape, such as a Y-shape as shown in FIGURE 4, or a propellor shape, keyhole shape, slot, etc.) and larger counterbore 22 leading to the capillary from the plateau. Back or top plate '7 is sealed against and spaced from the front plate by gasket 6 and shim 16, the former being ringshaped and located near the periphery of the opposing faces of the two plates and the latter being disc-shaped and located concentric with the two plates. Relatively unconstricted region 12 between the two plates is interrupted at intervals by constricted regions 15 between the opposing face of the back plate and plateaus of the protrusions from the front plate. The back plate is partitioned on top by outer wall 19 and inner wall 29 into annular chamber 8 and central chamber 9. The annular chamber communicates with the constricted regions between the two plates through counterbored apertures 1d, consisting of terminal capillary 2.3 and counterbore 24, and the central chamber communicates with the intervening relatively unconstrictcd region through holes 11. The two plates are retained in place by cap 18 threaded onto the end of the back plate. The upper part of the housing (not shown) receives suitable piping or other supply means for separate connection to the two chambers, which may constitute distribution or filtering spaces as desired. Pin 14 through cylindrical openings (opening 25 in the front plate and opening 26 in the back plate) near one edge of the plates ensures the desired alignment of the two plates.

FIGURE 2 shows the plan of the front plate. Appearing in this view are eight plateaus, each concentric with an extrusion orifice and uniformly spaced about a circle inside the outer gasket. FlGURE 3 shows the appearance of the back plate sectioned as indicated on FIGURE 1. Visible are the concentric outer and inner walls, the capillaries and counterbores of eight apertures spaced uniformly on a circle between the two walls, and four openings located within the central chamber defined by the inner wall.

Operation of the described apparatus in the practice of this invention is readily understood. Separate polymers are supplied to the inner and the outer chambers, respectively, of the back plate; the former flows through the openings into the relatively unconstricted space 12 between back and front plates, through the relatively constricted regions between the plateaus and the opposing plate face, and through the extrusion orifices to form the fins of a filament while the latter passes first through the apertures in the back plate and directly into and through the aligned orifices in the front plate to form the stem of the component.

The structure and operation of the apparatus described above are covered in the pending application of I. J. Kilian, Serial No. 519,031, filed June 30, 1955, and now Patent No. 2,936,482 dated May 17, 1960, pertinent portions of which are incorporated herein by reference.

FIGURES 5-9 illustrate a single-hole spinneret for the production of fiat or ribbon-like filaments of this invention. Spinneret plate '39 is adapted to be secured to back plate 38 which is connected by suitable piping (not shown) to sources for two different polymers, and which contains therein conventional filter pack (not shown). Back plate 33 is provided with chambers 40 and 40' separated by wall 41, which are connected to passageways 42 and 43, respectively, and shallow chambers 44 and 45, respectively. Spinning fluid passes from the latter chambers through a series of short grooves 46 and 46' to slot 47 which curves inwardly and downwardly as shown in FIGURE 8, to the outlet orifice 48. The center grooves 4-6 leading from chamber 44 and the end rooves 46 leading from chamber 45 are blocked by inserts 49 and 50, respectively, whereby to channel the two spinning solutions in overlapping relation to produce the type of filament shown in FIGURE 13. Spinneret plate 39 is fastened to back plate 38 by bolts 51 screw-threaded at 52 to back plate 33, gasket 53 serving to prevent leakage between the plate when pressed into position as the plates are assembled.

Although FIGURES 59 illustrate one form of apparatus for producing multi-component ribbon filaments, other forms may be used. The apparatus of FIGURES 5-9 is adapted to produce filaments with one component lapped over another, as in FIGURE 13, to give additional adhesive strength. Where the components will normally bond strongly to each other, a lap joint is unnecessary, and the filaments may be made by the use of the apparatus of FEGURES 1-3, the spinning orifice then being a slit, the center portion of which is formed by polymer flowing from inner capillary 23 into center portion of bore 22, the other polymer forming the tips by passing on the outside of the first polymer.

The examples, in which parts, proportions, and percentages are by weight, unless otherwise specified, are illustrative of modes of carrying out the invention.

Example I A spinneret similar to that shown in FIGURES 5, 6, 7, 8, and 9 is constructed. Poly(ethylene terephthalate) of n,. (relative viscosity) 29 is fed to chamber as and extruded as the stern (central portion) of a ribbon-shaped filament. Poly(hexamethylene adipamide) (66 nylon) of n (relative viscosity) 35 is fed to chamber 40' and extruded as the two fins of the composite filament. The polymers are extruded at 301 C. and the yarn is Wound up at 1000 y.p.m. A picture of a typical cross section of the as-spun ribbon is shown in FIGURE 13. The width/ thickness ratio of the fin is about 7/ 1.

The yarn is drawn 3 (200% draw) in a dry state over an C. pin and then boiled off under about 0.01 g.p.d. (grams per denier) tension. The boiling causes about 30% shrinkage and causes the fins to convolute helically about the core (due to their smaller extent of shrinkage) at a rate of about 30 ruiiles per inch. The angular displacement of the fins is about 0.4/micron. The yarn that is thus bulked by the ruffled fins has a much lower apparent density than an unshrunk sample of the drawn yarn. The bulked yarn has a dry tenacity of 2.4 g.p.d. (grams per denier), a dry elongation of 65% and an Mi (initial modulus of elasticity) of 12.

The above spin is repeated under the same conditions except that a copolymer of 66, 6 and 6-10 nylon (121:1 ratio by weight) of It (relative viscosity) 32 is extruded as the stem. Upon processing similar to that described above, the stem shrinks more than the 66-nylon fins and the yarn is likewise bulked by convoluting of the fins.

Example II A spinneret similar to that shown in FIGURES l, 2, and 3 is constructed having seventeen Y-shaped orifices (21) (shown as greatly magnified) as illustrated in FTGURE 4-, each located in a 62.5 mil diameter counterbore (22) that is concentric to a 135 mil diameter plateau (4).

A copolym r, poly(ethylene terephthalate/isophthalate) 90/ composition by Weight with an n (relative viscosity) of 30 is fed to chamber (8) and extruded as the stem of a composite filament. Poly(et'nylene terephthalate) of n (relative viscosity) 16 is fed to chamber 9 and extruded as the fins of the composite filaments. The polymers are extruded at 290 C. and wound up at 1500 y.p.m. The as-spun yarn is run over a water wick and drawn 2.7 on a 70 C. pin to an elongation of 6%. A typical drawn cross section is shown in FlG-URE 12. The Width/thickness ratio of the fins is about 2.8/1. A skein of the drawn yarn is restrained so that it shrinks only 40% upon boiling 10 minutes in Water. The lower molecular Weight fins shrink less than the stem and are thereby convoluted. Over 75% of the total fin length is highly convoluted and has about 150 rufiies per inch. The rufiled fins have an angular displacement of 2/rniown. The dried yarn has a permanent low apparent density, resists crushing and packing, and has a dry tenacity of 0.6 g.p.d., a dry elongation of 237%, and Mi of 1.6.

Another portion of the as-spun yarn is Water wicked and drawn 2.7 over a 90 C. pin. The yarn is restrained and shrinks 30% in boiling water and gives a rufiled product similar to above.

Another portion of the as-spun yarn is stored in a Dry Ice chest until just prior to drawing. A 2.4x draw of the cold dry yarn over a 98 C. pin gives a yarn which affords rufile and bulk equivalent to above when permitted to shrink only in boiling water.

In addition to ribbonand Y-shaped cross sections, the filaments may be spun with propeller blade cross section from an orifice having a central hole connecting two slits, or they may be cruciform, keyhole-shaped or otherwise shaped with fins. For ease of orifice manufacture, instead of complete slits, the fin-forming portion of the spinning orifice may be composed of a series of closely drilled holes from which the spinning fluid passes and then merges outside the spinning orifice in much the same way as if it were spun through a slit.

The filaments of this invention derive their utility from the relatively high frequency with which the fins convolute or change direction on a filament so that close packing between two adjacent filaments is not possible. With the relatively coarse crimped filaments of the prior art, such packing is possible.

The eifective volume of the filaments of this invention is a function of the length of the fins, the number of fins, the fraction of the fins that are convoluted and the rate at which the fins change direction as expressed by the angular displacement.

It is preferred that the filaments of this invention have an angular displacement of at least 0.5 and at least convolutions per inch. The filaments may be used as continuous filaments or as staple fibers for the production of yarns of textile denier, e.g., 30 to 8000, which are useful in the production of bulky woven or knitted goods. The filaments may also be used in the manufacture of felting.

Suitable pairs of components for use in this invention can be found in all groups of synthetic fiber-forming materials, which have the desired physical properties and in addition possess sufficient difference in shrinkage between the two selected components so that a rufiled fiber can be obtained. The minimum difierence in shrinkage is preferably about 2%.

Because of their commercial availability, ease of processing and excellent properties, the condensation polymers and copolymers, e.g., polyamides, polysulfonamides and polyesters and particularly those that can be readily melt spun are preferred for application in this method. Suitable polymers can be found, for instance, among the fiber-forming polyamides and polyesters which are described, e.g., in US. Patents 2,071,250; 2,071,253; 2,130,- 532; 2,130,948; 2,190,770; 2,465,319 and in other places. The preferred group of polyamides comprises such polymers as poly(hexamethylene adipamide), poly(hexamethylene sebacamide), poly(epsilon-caproamide), and the copolymers thereof. Among the polyesters that may be mentioned, besides poly(ethylene terephthalate), are the corresponding copclymers containing sebacic acid, adipic acid, isophthalic acid as Well as the polyesters containing recurring units derived from glycols with more than two carbons in the chain.

Other groups of polymers useful as components in filaments of the present invention can be found among the polyurethanes or the polyurcas as well as among the polyvinyl compounds, including such polymers as polyethylene, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, and similar polymers.

The polymer used as the stern should have a shrinkage (as determined by treatment with boiling Water for 5 minutes) of at least 2% and preferably more than 10%, although the exact value will depend upon the shrinkage of the fins. Higher shrinkages are preferred for the stem member in order to gain the greatest amount of bulk. In order to have good ruflle retention, the stem polymer should have a high tensile recovery and initial modulus.

The polymer used as the lower shrinking member of the composite filament, i.e., ordinarily the polymer used for the fin, should have as low a shrinkage as possible under the processing conditions used, preferably less than 90% the shrinkage of the higher shrinking component. The exact shrinkage value required will depend upon the other component inasmuch as it is the difference in shrinkage that controls the ruffie. A shrinkage in boiling water of no more than 5% is preferred.

A preferred class of polymers for use as a lower shrinking member of composite filaments are those condensation polymers containing an aromatic group intralinear to the polymer chain. These include polyamides and polyesters made from such dibasic acids and diamines as: terephthalic acid, isophthalic acid, p-xylylene diamine, p-bis(ethyl amino) benzene, p-phenylene-diamine, 4,4- diamino diphenylmethane, benzene diacetic acid, 4,4- diaceto diphenylmethane to name a few and other monomers as desired. The physical properties, such as melting point or solubility of the homopolymer containing the preferred aromatic constituent may be modified as desired by copolymerization. The presence of as little as 20 mol percent of the aromatic monomer in the low shrinking polymer is effective, but 25 to mol percent is preferred. The polymer components of the constituents used in a copolymer should preferably be isomorphous, in order to maintain as low as shrinkage as possible.

A low molecular weight polymer is preferred for the fins. The molecular weight of a polymer used for the production of synthetic fibers is usually a compromise between the various physical properties desired in the product, the ease of making the fiber including such processes as spinning, drawing, etc., and possibly the production of the polymer itself. Physical properties such as tenacity generally increase with increasing molecular Weight. The viscosity of a concentrated solution or melt of the polymer also increases with increasing molecular Weight. However, too low a molecular weight polymer may be as difficult to spin because of its low viscosity as a very high molecular Weight polymer may be due to its very high viscosity so that an intermediate value of molecular weight may well be selected for use.

The lowest molecular weight poly(hexamethylene adipamide) that can be commercially spun and drawn as single component filaments is about that which corresponds to a relative viscosity of 27, but this value is too low for the production of first-class yarn, and relative viscosity values of 36 and higher are now used. The commercially accepted molecular weight levels of other polyamides will vary with the specific polymer, but, in general, they will be similar to the above.

Poly(ethylene terephthalate) of relative viscosity of 22 is about the minimum for commercial spinning and drawing, but relative viscosity 27-33 are currently used in commerce to avoid denier non-uniformities, spinning and drawing breaks, and low tenacities that are prevalent when using the minimum molecular weight.

For use as the low shrinking fins of the filaments of this invention, polymers having molecular Weights which would give a relative viscosity of about 6 to 20 can be used. Relative viscosities of 10 to for polyamides and 10 to 19 for polyesters are preferred. These levels are defined for the purpose of this invention as low molecular weight. These values correspond to about 75% and preferably less of the molecular weight of the polymers desired for commercial spinning and drawing of single component filaments.

The exact relative viscosity values of other polymers for use in this invention will depend upon the relationship between absolute molecular weight and relative viscosities of the given polymer, but the minimum acceptable level for commercial spinning will be apparent to those skilled in the art and a value of 75% or less of that will be preferred in this invention.

The lower values of molecular weight polymers useful as low shrinkage components of this invention will be limited by the ability to spin the polymer and the physical properties of the composite yarn. The preferred polymers are especially useful in this regard since those having an aromatic group in the polymer chain generally have a higher melt viscosity for a given relative viscosity than do the non-aromatic polymers. Such higher melt viscosities afford better spinning of these polymers.

The desired difference in shrinkage between the two components can be brought about by a number of processes. In some cases the extent of shrinkage will depend upon the drawing conditions. For example, when cold drawn, poly(ethylene terephthalate) shrinks more than a cold drawn nylon, but when a hot plate is included after a hot pin drawing, the shrinkage tendencies are reversed and the polyester becomes the lower shrinking. Such a step is termed length stabilization. It is considered that this is due to a more rapid rate of crystallization of the polyester, and this may be due to the difference between the apparent minimum crystallization temperature of the two polymers determined as described in US. 2,578,899. A difference in crystallization which may reverse or enhance the difference in shrinkage may also be brought about by the presence of a plasticizer in one component which will enable it to be crystallized more readily. The addition of certain substances also increased the rate of crystallization. For example, the presence of 4 10 particles of BaSO per gram of poly(ethylene terephthalate) doubles the rate of crystallization of the polymer. In addition, certain polar organic liquids which are latent solvents for the amorphous regions of one of the components may be used to preferentially crystallize that component and reduce its normal shrinkage.

The composite filaments have been produced in the examples by the melt-spinning technique. Naturally, also any other spinning method like plasticized melt spinning, dry spinning, wet spinning, can be employed successfully. In some instances, particularly when the melting behavior or the solubility of the components in a combination would not permit spinning the components by similar methods, a combination of dissimilar methods is indicated. Thus, for instance, one component can be spun as a solution in a high boiling solvent or as a plasticizer melt, while the other component is extruded as the molten polymer. In these instances, the solvents or plasticizers may be Wholly or partially removed subsequently, preferably by washing them out by the help of low boiling solvents.

The composite filaments of this invention are substantially unruffled after drawing and/or the application of the length stabilization treatment but contain, however, a potential convolution. The rufile or twist can be developed in these filaments very readily by a suitable aftertreatment. The filaments containing the potential convolution can be processed as any ordinary uncrimped continuous filaments or staple fibers to worsted or knitted goods. The rufile can then be imposed on the filaments at any time by a suitable relaxing or shrinkage treatment. This shrinkage treatment was performed in the foregoing examples by exposing the composite filament containing the potential ruflle to hot water or steam. Which of these after-treatments for bringing about the crimp are chosen depends mostly on the properties of the components forming the composite filaments and on the final properties which are desired in the crimped filaments. In general, the temperature applied in the bulking procedure should be higher than the apparent second-order transition temerature (Tg) of the polymers forming the composite filament in order to achieve the favorable results of the invention. A convenient method for measuring this temperature is shown in US. Patent No. 2,578,899. Since water acts as a plasticizer in many polymers, thus lowering the apparent second-order transition temperature (Tg), this should also be considered in measuring (Tg) and in selecting the appropriate bulking method and temperature. Other factors influencing the optimum condition for bulking the composite filaments of this invention are, for instance, the spinning, drawing, and length stabilizing conditions used and also other factors, for instance, whether the composite filament is processed as continuous filament or as staple or as a woven or knitted textile fabric. Therefore, by varying the after-treating conditions for bringing about the rufile, also the properties and appearance of the ruffled filaments can be varied to a great extent in any desired way.

In general, the composite filaments are drawn from about 2 times to about 8 times their original lengths. lrior to drawing, the filaments are attenuated; that is, they are slenderized by pulling the freshly extruded filaments away from the orifice at a rate faster than the extrusion rate. The drawing or orientation step is in addition to attenuation but also has a slenderizing effect. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymers used in the composite filament, upon the shape of the composite filament and spinning speed.

In the hot relaxing treatment of this invention used to develop the potential rufiie, the medium may be anyinert atmosphere capable of being heated to a temperature of about C. Thus, the filaments may be heated in air, nitrogen, hot or boiling water, carbon dioxide, or any gaseous or liquid media inert to the polymers in the composite filaments. The temperature used is generally in the neighborhood of 100 C., but it may be lower or higher. For example, any temperature above about 50 C., but below the melting point of the lowest melting polymeric constituent in the composite fiber, may be used. Generally, a temperature in the range of about 50 C. to about C. is used with convenience.

The length of time that the composite filaments are subjected to the hot, relaxing treatment is not critical, because the rufile develops immediately and spontaneously.

The relatively high frequency of the rufiles of the fins of these products confer bulk and resistance to packing that is not attained by the crimped filaments of the prior art. The filaments of this invention may be fabricated before shrinking as continuous filament or cut staple and bulk developed in the fabric with the finishing step. Alternatively, the fibers may be shrunk to give a prebullted filament, yarn, or staple before fabrication.

Although the invention has been described mainly in connection with two-component fibers, it will be understood that three or more components may be used, e.g., in making the fiat filament of Example II. While it is preferred that both components (or more, if more than two are used) be synthetic linear polymers, the invention broadly comprehends within its scope filaments in which only one component, preferably the stem of the filament, is a synthetic linear polymer.

The claimed invention:

1. An improved bulked composite filament comprising a first longitudinally extending stem portion of a first synthetic linear polymeric composition in a substantially rounded constant area transverse cross section, and at least one additional portion of a second synthetic linear polymeric composition longitudinally disposed along and joined with said first portion, said second portion having a wide thin ribbon-like form with two longitudinally extending side edges, said second portion joined to said first portion along one of said two side edges, the thickness of said first portion significantly greater than the thickness of said ribbon-like second portion, the other of said two side edges of said second portion arranged in a random undulated configuration relative to said first portion of said filament to form a non-uniform rufile disposed along the length of said filament to increase its bulk, said other side edge having an angular variation with respect to the filament of at least O.l per micron of filament length and at least 30 reversals of direction per inch of filament length.

2. An improved bulked composite filament comprising a first longitudinally extending stern portion of a first synthetic linear polymeric composition in a substantially rounded constant area transverse cross section, and one additional portion of a second synthetic linear polymeric composition longitudinally disposed along and joined with said first portion, said second portion having a wide thin ribbon-like form with two longitudinally extending side edges, said second portion joined to said first portion along one of said two side edges, the thickness of said first portion significantly greater than the thickness of said ribbon-like second portion, the other of said two side edges of said second portion arranged in a random undulated configuration relative to said first portion of said filament to form a non-uniform rufiie disposed along the length of said filament to increase its bulk, said other side edge having an angular variation with respect to the filament of at least O.l per micron of filament length and at least 30 reversals of direction per inch of filament length, said filament having a transverse cross section at any point along its length of substantially a icy-hole shape.

3. An improved bulked composite filament comprising a first longitudinally extending stem portion of a first synthetic linear polymeric composition in a substantially rounded constant area transverse cross section, and at least one additional portion of a second synthetic linear polymeric composition longitudinally disposed along and joined with said first portion, said second portion having a wide thin ribbon-like form with two longitudinally extending side edges, said second portion joined to said first portion along one of said two side edges, said first and second portions so proportioned with respect to each other that the center of gravity of the filament at any given tra.sverse cross section lies within said first portion, the other of said two side edges of said second portion arranged in a random undulated configuration relative to said first portion of said filament to form a non-uniform rufiic disposed along the length of said filament to increase its bulk, said other side edge having an angular variation with respect to the filament of at least 0.1 per micron of filament length and at least 30 reversals of direction per inch of filament length.

References Cited in the file of this patent UNITED STATES PATENTS 1,884,069 Mendel Oct. 25, 1932 2,002,153 Mendel May 21, 1935 2,378,183 Caldwell June 12, 1945 2,439,814 Sisson Apr. 20, 1948 2,439,815 Sisson Apr. 20, 1948 2,637,893 Shaw May 12, 1953 2,682,292 Nagin June 29, 1954 FOREIGN PATENTS 176,323 Switzerland July 1, 1935 

1. AN IMPROVED BULKED COMPOSITE FILAMENT COMPRISING A FIRST LONGITUDINALLY EXTENDING STEM PORTION OF A FIRST SYNTHETIC LINEAT POLYMERIC COMPOSITION IN A SUBSTANTIALLY ROUNDED CONSTANT AREA TRANSVERSE CROSS SECTION, AND AT LEAST ONE ADDITIONAL PORTION OF A SECOND SYNTHETIC LINEAR POLYMERIC COMPOSITION LONGITUDINALLY DISPOSED ALONG AND JOINED WITH SAID FIRST PORTION, SAID SECOND PORTION HAVING A WIDE THIN RIBBON-LIKE FORM WITH TWO LONGITUDINALLY EXTENDING SIDE EDGES, SAID SECOND PORTION JOINED TO SAID FIRST PORTION ALONG ONE OF SAID TWO SIDES EDGES, THE THICKNESS OF SAID FIRST PORTION SIGNIFICANTLY GREATER THAN THE THICKNESS OF SAID RIBBON-LIKE SECOND PORTION, THE OTHER OF SAID TOW SIDE EDGES OF SAID SECOND PORTION ARRANGED IN A RANDOM UNDULATED CONFIGURATION RELATIVE TO SAID FIRST PORTION OF SAID FILAMENT TO FORM A NON-UNIFORM RUFFLE DISPOSED ALONG THE LENGTH OF SAID FILAMENT TO INCREASE ITS BULK, SAID OTHER SIDE EDGE HAVING AN ANNULAR VARIATION WITH RESPECT TO THE FILAMENT OF AT LEAST 0.1* PER MICRON OF FILAMENT LENGTH AND AT LEAST 30 REVERSALS OF DIRECTION PER INCH OF FILAMENT LENGTH. 